AU6922000A

AU6922000A - Composite coating with improved chip resistance

Info

Publication number: AU6922000A
Application number: AU69220/00A
Authority: AU
Inventors: John Gilbert; Rock Mc Neil
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 1999-11-17
Filing date: 2000-08-21
Publication date: 2001-05-30
Anticipated expiration: 2020-08-21
Also published as: WO2001036114A1; KR100622790B1; ES2208412T3; MXPA01011994A; DE60005989D1; BR0011637A; PL356101A1; AU774366B2; JP2003513795A; EP1230038A1; KR20020053859A; US6210758B1; DE60005989T2; CA2373004A1; ATE251952T1; EP1230038B1

Abstract

The invention provides a method of coating a substrate with first a layer of a chip resistant primer composition that has as a resinous portion a polyurethane polymer having a glass transition temperature of 0° C. or less and, optionally, a second component that has reactive functionality; and next with a layer of a thermosetting primer composition including a polyurethane polymer having a glass transition temperature of 0° C. or less, an acrylic polymer having a glass transition temperature that is at least about 20° C. higher than the glass transition temperature of said polyurethane polymer, and a crosslinking component that is reactive with at least one of the polyurethane polymer and the acrylic polymer; and finally with at least one layer of a topcoat composition. The reactive functionality of the second component is reactive with at least one polymer selected from the group consisting of the polyurethane polymer of the chip resistant primer composition, the polyurethane polymer of the thermosetting primer composition, the acrylic polymer of the thermosetting primer composition, and combinations thereof.

Description

WO 01/36114 PCT/USOO/22919 COMPOSITE COATING WITH IMPROVED CHIP RESISTANCE 5 Field of the Invention The oresen: invention relates 7o comoosite crimer coatinas that provide chic resistance and to aaueous -rimer compositions zre: provide sucn composloe coatings. Background o: one Invention 10 Coating finishes, oarticularly exterior coating finishes in the automotive industry, are oenerally applied in two or more distinct -avers. One or more savers o: crime coatzng composition may be applied to the unpainted substrate first, followed by one or more topcoat layers. Each of the layers 15 supplies important properties toward the durability and appearance of the composite coating finish. The primer coating layers may serve a number of purposes. First, the primer coating may be applied in order to promote adhesion between the substrate and the coating. Secondly, ohe primer 20 coating may be applIied in order to improve physical properties of the coating system, suc as corrosion resistance or impact strength, especially for improving resistance to travel chipping. Third, the primer coating may be arclied in order to improve the acrearance of the coatna 25 by providing a smooth laver upon wic he topcoat savers may be applied. The topcoat layer or layers contribute other SUBSTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 properties, such as color, appearance, and light stabilization. In the process of finishing the exterior of automotive vehicles today, metal substrates are usually first coated 5 with an eleccrocoat primer. While the electrocoat primer provides excellent surface adhesion and corrosion protection, it Is often desirable to apply a second primer layer. The second primer layer provides additional properties not available from the electrocoat primer. Resistance to gravel 10 chipping is one cr the critical properties provided by the second primer layer. The second primer layer may also enhance the corrosion protection of the finish and provide a smoother surface than the electrocoat primer. The second primer also serves to provide a barrier layer between the 15 electrocoat primer layer, which usually contains aromatic moieties and other materials that can cause yellowing on exposure to sunlight, and the topcoat. Mitsuji ec al, U.S. Patents 5,281,65, 5,227,422, and 4,948,829, all of which are incorporated herein by reference, 20 disclose automotive basecoat coating compositions containing polyurethane resin emulsion, a second resin emulsion than can be an acrylic resin, and a crosslinking agent. In Mitsuji '829, the Colvurethane resin is prepared by dispersing an isocvanate-functional prepolymer and having the water react 25 with the isocyanate groups to chain-extend the prepolymer. SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 The prepolymer is prepared using an aliphatic diisocyanace, a polyether or polyester diol, a low molecular weight polyol, and a dimethylolalkanoic acid. in Mitsuji '655 and '422, the polvurechane resin Is prepared by reactino an aliphatic 5 poi:socvanate, a high molecular weich: polyol, a dimethvlolalkanoic acid, and, optionally, a chain extender or terminator. Because the Mitsuji patents are directed Tc basecoa: coatings, these patents provide no direction for preparing compositions that have the chip resistance and 10 other trcpercies required for primer coating layers. Hatch et al., U.S. Patent 5,817,735, incorporated herein by reference, discloses an aaueous primer composition for golf balls that includes a polyurethane dispersion and an acrylic dispersion. The primer has a very low content of 15 volatile organic solvent, which is important for minimizing regulated emissions from the coating process. The Hatch patent, however, does not disclose a curable (thermoset:ing) composition. More import:anty, the golf ball primers of the Hatch patent do no: provide the properties, such as 20 resistance to stone chipping and corrosion protection, that are reauired of an automotive primer. While the primer composiion may be formulated tc provide good resistance to gravel chipping for a vehicle body, some areas of th vehicle are particularly prone to 25 gravel chipping. These areas include the A pillars (pillars qIIRqTITI IT= qHF=T (RULE 261 WO 01/36114 PCT/USOO/22919 on either side of the windshield), the front edge of the roof, the leading edge of the hood, and rocker panels. In these areas, it is advantageous to provide an additional layer of a chip-resistant primer before the primer that is 5 applied to the rest of the vehicle body to obtain increased protection against stone chipping. In general, primer compositions applied for this purpose are solventborne, thermosetting compositions. While these chip-resistant layers have worked well with solventborne primer 10 composizions, there remains a need for a chip-resistant primer composition compatible with aqueous primer compositions. Further improvements in chip resistance of the primer are also necessary. It would be desirable, therefore, to have a composite 15 primer coating that includes an upper layer of an aqueous body primer composition that provides improved resistance to stone chipping and other properties that are important for an automotive primer and an under layer of a chip-resistant primer layer, compatible with the upper primer layer, 20 particularly for wet-on-wet applications of the upper primer layer over the chip resistant primer layer, that provides additional chip resistance in particular areas of the vehicle body. :n addition, :or environmental and regulatory considerations, it would be desirable to produce both the 25 upper primer layer and the lower layer of chip resistant 4 l]RlTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 primer from compositions having a very low content of volatile organic solvent. Summary of the Invention The present invention provides a method of applying a 5 composite coatina to an automotive vehicle. In che method, a layer of a chip resistant primer composition is applied to at least one area of ohe vehicle and the applied primer composition forms a chip resistant primer layer. The chip resistant primer composition includes as the resinous portion 10 a polyurethane polvmer having a class transition temperature of 0 0 C or less and, optionally, a second component that has reactive functionality. Then, a thermosetting primer composition is applied to the vehicle. The reactive functionality is reactive with either the 15 polyurethane polymer of the chip resistant primer composition or with one of the components of the thermosetting primer comoostion. The thermosettinq crmer composition includes a polyurethane polymer, an acrylic polymer, and a crosslinking component that is reactive with a: least one of the 20 polyurethane polymer and the acrylic polymer. The polyurethane polymer has a glass transition temperature of 0 0 C or less. The acrylic polymer has a qlass transition temperature that is at least abou: 200C higher than the glass transition temperature of polvurethane resin. The 25 polyurethane polymer of both primers and acrylic polymer are SUBSTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 preferably dispersed or emulsified in an aqueous medium. As used herein, "emulsion" or "dispersion" will each be used to refer both to dispersions and emulsions. The invention further provides a composite coating 5 having a first layer of a chip resistant primer, a second primer layer over the first layer of chip resistant primer, and a topcoat layer over the second primer layer. The first layer of chip resistant primer is formed from a composition including as the resinous portion a polyurethane polymer 10 having a qlass transition temperature of 0 0 C or less and, optionally, a second component that has reactive functionality. The reactive functionality is reactive with either the polyurethane polymer of the chip resistant primer composition or with one of the components of the primer 15 composition forming the second primer layer. The second primer layer is the product of a primer composition including a polyurethane polymer has a glass transition temperature of 0 0 C or less, an acrylic polymer has a glass transition temperature that is at least about 20 0 C higher than the glass 20 transition temperature of polyurethane resin, and a crosslinking component. Detailed Description of the Invention A layer of the chip resistant primer composition is applied to at least one area of the vehicle. In a preferred 25 embodiment, the chip resistant primer composition is applied 6 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 to one or more of the following vehicle areas: the A pillars (pillars on either side of the windshield), the front edge of the roof, the leading edge of the hood, the front bumper, the rocker Danels, and combinations of these. 5 The chin resistant primer comnosition Includes as the resinous portion polyurethane polymer having a glass transition temperature of 0 0 C or less and, optionally, a second component that has reactive functionality. The polyurethane polymer used has a glass transition temperature 10 of about .O 3_ r less, preferably about -20 0 C or less, and more preferably about -30 0 C or less. The glass transition temperature of the polyurethane of the invention is in the range of from about -80 0 C to about 0 0 C, more preferably from about -65 0 C to about -10 0 C, still more preferably from about 15 65'C to about -30'C, and even still more preferably from about -600C to about -35 0 C. The weight average molecular weight of tne polyurethane is preferably from about 15,000 to about 60,000, more preferably from about 15,000 to about 60,000, and even more 20 preferably from about 20,000 to about 35,000. Polvurethanes are prepared by reaction of at least one polvisocyanate and at least one polyol. The reactants used to prepare the polyurethane are selected and apportioned to provide the desired glass transition temperature. Suitable SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 polivsocvanaces include, wt'cout mioation, aiphatic linear and cyclic polyisocyanates, preferably having up to 18 carbon atoms, and substituted and unsubstituted aromatic oolvisocvanates. Illustrative examples include, without 5 imi:a:ion, eohylene diisocvanate, I,2-iisocvanacopropane, ,3-disocyanaopropane, 1,-butylene diisocyanate, lysine diisocyanaze, I,--methylene bis (cvclohexvl isocyanace) isoporone diisocyanace, toluene diisocvanates (e.g., 2,4 'oluene diisocyanaoe and 2,6-coluene diisocvanate) 10 diphenvlmethane 4,4'-diisocyanate, metvyenebis-4,4' isocyanacocyclohexane, 1,6-hexamethylene diisocyanate, p phenylene diisocyanate, tetramethyl xylene diisocyanate, meta-xylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, cyclohexane 15 1,3- and -1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, and combinations of two or more of these. Diure:s, allophonates, isocvanurates, carbodiimides, ant other such modifications of: _ese isocvanaces can also be used as :he polvisocyanaces. In a preferred embodiment, the 20 polvisocvanates include methylenebis-4,4 'I isocyanazocyclonexane, ,-hexamethy diisocyanate, 1,12 dodecamethvlene diisocvanate, and combinations thereof. is parzicularl: preferred to use at leas: one ac,o-alkylene diisocvanate having four or more carbonS, oreferablv 6 or 25 more carbons, in the alkylene group. Combinations of two or S SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 more polyisocyanates in which one of the polvisocyanates is 1,6-hexamethylene diisocyanate are especially preferred. The polyol or polyols used to prepare the polyurethane polymer can be selected from any of the polyols known to be useful in preparing polvurethanes, including, witnout limitation, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentvl glycol, 1,3-propanediol, 1, pentanediol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene 10 glycol, propylene glycol, dipropylene glycol, glycerol, cyclohexanedimethanois, 2-methyl-2-ethyl-1 ,3-propanediol, 2 ethyl-1,3-hexanediol, thiodiglycol, 2,2,4-trimethyl-1,3 pentanediol, cyclohexanediols, trimethylolpropane, trimethylolethane, and glycerin; polyester polyols such as 15 the reaction products of any of the foregoing alcohols and combinations thereof with one or more polycarboxylic acids selected from malonic acid, maleic acid, succinic acid, glutario acid adipic acid, azelaic acid, anhydrides thereof, and combinations thereof; polyether polyols, such as 20 polyethylene glycols and polypropylene glycols; and combinations of such polyols. Polvols having two hydroxyl groups are preferred. The polyurethane is preferably prepared using one or more polvester polyols. In a referred embodiment, the polvester polVol is the reaction product or a 25 mixture that comprises neopentyl glycol and adipic acid. 9 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 While it is possible to prepare a nonionic dispersion of the polyurethane, the polyurethane dispersion is preferably anionic. Acid-functional polyurethanes that can be salted to form anionic discersions or emulsions may be synthesized by 5 including a monomer having acid functionality, such as, without limitation, dialkylpropionic acids including dimethylolpropionic acid, and alkali metal salts of amino acids such as taurine, methyl taurine, 6-amino caproic acid, glycine, sulfanilic acid, diamino benzoic acid, ornithine, 10 lysine and 1:1 adducts of sultones, such as propane sultone or butane sultone, with diamines, such as ethylene diamine, hydrazine, or 1,6-hexamethylene diamine. The hydroxyl groups react to form the urethane linkages while the acid group remains unreacted in the polyurethane polymerization. 15 Suitable polyurethane polymers can be prepared by any of the known methods. In one method for preparing polyurethane polymers, the polyisocyanate component is reacted with an excess of equivalents of the polyol component to form a hydroxyl-functional polyurethane polymer. Alternatively, an 20 excess of equivalents of the polyisocyanate component can be reacted with the polyol component to form an isocyanate functional prepolymer. The prepolymer can then be reacted further in different ways. First, the prepolymer can be reacted with a mono-functional alcohol or amine to provide a 25 non-functional polyurethane polymer. Examples of mono 10 qIIRRTITIJTF RHFET (RULE 26i WO 01/36114 PCT/USOO/22919 functional alcohols and amines that may be used include polyethylene oxide compounds having one terminal hydroxyl group, lower mono-functional alcohols having up to 12 carbon atoms, amino alcohols such as dimethylethanolamine, and seconoarv amines such as diethvlamine and aimetnvaamine. Seccadly:, ohe prepolymer can be reacted with a polyfunccional polol, polyamine, or amino alcohol compound to provide reactive hydrogen functionality. Examples of such polyfunctional compounds include, without limitation, the 10 polvols already mentioned above, including trils such as trimethylolpropane; polyamines such as ethylenediamine, butylamine, and propylamine; and amino alcohols, such as diethanolamine. Finally, the prepolymer can be chain extended by the water during emulsification or dispersion of 15 the prepolymer in the aqueous medi, n. The prepolymer is mixed with the water after or during neutralization. The colvurethane may be polvmerized without solvent. Solvent may be included, however, if necessary, when the polyurethane or prepolymer product is of a high viscosiy. 20 If solvent is used, the solvent may be removed, partially or completely, by distillation, preferably af:er the polyurethane is dispersed in the water. The polyurethane may have nonionic hydrophilic groups, such as poiyethylene oxide groups, that serve to stabilize the dispersed polyurethane 25 polymer. In a preferred embodiment, however, the 11 qIRqTITTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 polyurethane polymer is prepared with pendant acid groups as described above, and the acid groups are partially or fully salted with an alkali, such as sodium or potassium, or with a base, such as an amine, before or during dispersion of the 5 polyurethane polymer or prepolymer in water. The chip resistant primer composition may also include a second component that has reactive functionality. The reactive functionality is reactive with either the polyurethane polymer of the chip resistant primer composition 10 or with one of the components of the thermosetting primer composition. When the chip resistant primer layer includes the second component, the composite coating has higher hardness, better cure and solvent resistance, and better intercoat adhesion. 15 In a preferred embodiment, the second component is a crosslinker reactive with active hydrogen functionality on at least one of the polyurethane polymer of the chip resistant primer, the polyurethane polymer of thermosetting primer composition, and the acrylic polymer of the thermosetting 20 primer composition. Examples of crosslinkers reactive with active hydrogen functionality include, without limitation, materials having active methylol or methylalkoxy groups, including aminoplast resins or phenol/formaldehyde adducts; blocked polyisocyanate curing agents; tris(alkoxy 12 q[IRRTITUTF SHEET (RULE 28I WO 01/36114 PCT/USOO/22919 carbonviamino) =riazines (available from Cytec Industries under the tradename TACT) ; and combinations thereof. Suitable aminoilast resins are amine/aldehyde condensates, preferably at least partially etherified, and 5 mos: Dreferabl- fullv etherif:ed. Melamine and urea are referred amines, but other -_razines, triazoles, diazines, guanidines, or guanamines may also be used to prepare he alkylated amine/aldehyde aminoplasz resins crosslinking agents. The aminoplast resins are preferably 10 amine/formaldehyde condensates, although other aldehydes, such as acetaldehyde, croctonaldehyde, and benzaldehyde, may be used. Non-limiting examples of preferred aminoplasz resins include monomeric or polymeric melamine formaldehyde resins, including melamine resins that are partially or fully 15 alkylated using alcohols that preferably have one to six, more preferably one to four, carbon atoms, such as hexamethoxv met.ylated melamine; urea-formaldehvde resins including methylci ureas and siloxv ureas such. as butvated urea formaldehvde resin, alkvlated benzoguanimines, guanyl 20 ureas, guanidines, biquanidines, polyguanidines, and he like. Monomeric melamine formaldehyde resins are particularly preferred. The preferred alkylated melamine formaldehyde resins are water miscile or water soluble. Examples of blocked polyisocyanates include isocyanurates of 25 toluene diisocyanate, isophorone diisocyanate, and .;IRSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 hexamethylene diisocyanate blocked with a blocking agent such as an alcohol, an oxime, or a secondary amine such as pyrazole or substituted pyrazole. The crosslinker is preferably included in the resinous 5 portion of the chip resistant primer at from about 2% by weight to about 30% by weight, and more preferably from about 5% by weight to about 20% by weight, a particularly preferably about 5% to about 15% by weight. The thermosetting primer composition includes a 10 polyurethane polymer, an acrylic polymer, and a crosslinking component that is reactive with at least one of the polyurethane polymer and the acrylic polymer. The polyurethane polymer has a glass transition temperature of 0*C or less. The polyurethane polymer may be any of those 15 already described above for the chip resistant primer. In a preferred embodiment, the same polyurethane polymer is included in both the chip resistant primer and in the thermosetting primer. The acrylic polymer of the thermosetting primer 20 composition has a glass transition temperature that is at least about 20'C higher than the glass transition temperature of polyurethane resin. The acrylic polymer is prepared according to usual methods, such as by bulk or solution polymerization followed by dispersion in an aqueous medium 25 or, preferably, by emulsion polymerization in an aqueous 14 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 medium. The acrylic polymer is polymerized from a monomer mixture that preferably includes an active hydrogen functional monomer and preferably includes an acid-functional monomer. Examples cf active hvdrogen-functional monomers 5 include, without imitation, hvdroxv-functiona monomers such as hydroxvethyl acrylate, hydroxvethyl methacrylate, hydroxyprop-y acrylace, hydroxypropyl methacrylate, hydroxybutyl acrylates, and hydroxybutyl methacrylates; and carbamate- and urea-functional monomers or monomers with 10 functicnal groups that are converted to carbamate or urea groups after polymerization such as, without limitation, those disclosed in U.S. Patent 5,866,259, "Primer Coating Compositions Containing Carbamate-Functional Acrylic Polymers," the entire disclosure of which is incorporated 15 herein by reference. Preferably, a sufficient amount of active hydrogen-functional monomer is included to produce an equivalent weight of 1000 or less grams per equivalent, more preferably 800 or less grams per equivalen:, and even more preferably 600 or less grams per equivalen:. 20 Ic is referred that the acrylic polymer is dispersed as an anicnic dispersion. Examples of suitable acid-funccional monomers include, without limitation, u, -echylenicallv unsaturated monocarboxvlic acids containing 3 co o ca5ron atoms, a,p-ethylenically unsaturated dicarboxylic acids 25 containing 4 to 6 carbon atoms and the anhydrides and 15 CIIRqtiTI ITF RWFFT IRULF 2RI WO 01/36114 PCT/USOO/22919 monoesters of these. Examples include, without limitation, acrylic acid, methacrylic acid, crotonic acid, maleic acid or maleic anhydride, itaconic acid or itaconic anhydride, and so on. A sufficient amount of acid-functional monomer is 5 included to produce an acrvlc polvmer with an acid number of at least abou: 1, and preferably the acrylic polymer has an acid number of from about i to about 10. in addition to the ethvlenically unsaturated monomer having acid functionality or used to generate acid 10 functionality in the finished polymer, one or more other ethylenically unsaturated monomers are employed as comonomers in forming the acrylic resins of the invention. Examples of such copolymerizable monomers include, without limitation, derivatives of x,3-ethylenically unsaturated monocarboxylic 15 acids containing 3 to 5 carbon atoms, including esters, nitriles, or amides of those acids; diesters of atp ethvlenically 'nsaturated dicarboxvlic acids containing 4 to 6 carbon atoms; vinyl esters, vinyl ethers, vinyl ketones, vinyl amides, and aromatic or heterocyclic aliphatic vinyl 20 compounds. Representative examples of acrylic and methacrylic acids, amides and aminoalkyl amides include, without limitation, such compounds as acrylamide, N-(1,1 dimethyl-3-oxobutvl)- acrylamide, N-alkoxv amides such as methylolamides; N-alkoxy acrylamides such as n-butoxy 25 acrylamide; N-aminoalkyl acrylamides or methacrylamides such 16 qI IRqTITIJT= RH~=FFT (RULE 261 WO 01/36114 PCT/USOO/22919 as aminomethylacrylamide, 1-aminoethyl-2-acrylamide, 1 aminopropyl-2-acrylamide, 1-aminopropyl-2-methacrylamide, N 1-(N-butylamino)propyl-(3)-acrylamide and 1-aminohexyl-(6) acrvlamide and 1- (N,N-dimethylamino)-ethyl-(2) 5 methacrylamide, 1-(N,N, -dimethylamino)-propyl- (3)-acrylamide and 1- (N, N-dimethylamino)-hexyl-(6)-mechacrylamide. Representative examples of esters of acrylic, methacrylic, and croconic acids include, without limitation, those esters from reaction with saturated aliphatic and 10 cycloaliphatic alcohols containing i co 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-bucyl, isobutyl, tert butyl, 2-ethylhexyl, lauryl, stearyl, cyclohexyl, trimethylcyclohexyl, tetrahydrofurfuryl, stearyl, sulfoethyl, and isobornyl acrylates, methacrylates, and crotonates; and 15 polyalkylene glycol acrylates and methacrylates. Representative examples of other ethylenically unsaturated oolymerizable monomers include, without limitation, such compounds as fumaric, maleic, and icaconic anhydrides, monoesters, and diesters. Polyfunctional 20 monomers may also be included to provide a partially crosslinked acrylic dispersion. Examples of polyfunctional compounds include, without limmiation, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, cecraenhylene glycol dimethacrylate, 1,6 17 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 hexanediol diacrylate, divinylbenzene, trimethylolpropane triacrylate, and so on. Representative examples of vinyl monomers that can be copolymerized include, without limitation, such compounds as vinyl acetate, vinyl propionate, vinyl ethers such as vinyl ethyl ether, vinyl and vinylidene halides, and vinyl ethyl ketone. Representative examples of aromatic or heterocyclic aliphatic vinyl compounds include, without limitation, such compounds as styrene, a-methyl styrene, vinyl toluene, tert 10 butyl styrene, and 2-vinyl pyrrolidone. After polymerization, the acid functionality is salted, preferably with an alkali or base, preferably an amine. Example of suitable salting materials include, without limitation, ammonia, monoethanolamine, ethylamine, 15 dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethvlhexylamine, ethylenediamine propylenediamine, ethylethanolamine, dimethylethanolamine, diethylethanolamine, 2-amino-2 20 methylpropanol, and morpholine. Preferred salting materials include 2-amino-2-methylpropanol and dimethylethanolamine. The acrylic polymers may be prepared as solutions in an organic solvent medium, preferably selected from water soluble or water-miscible organic solvents, and then 25 dispersed into water. After dispersion into water, the 18 SUBSTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 organic solvent can be distilled from the aqueous dispersion or emulsion. in a preferred method, the acrylic polymer is provided by emulsion polymerization. Preferably, a nonionic or an 5 anionic surfactant is used for the emulsion polymerization. Suitable surfactants include, without limitation, polyoxyethylenenonylphenyl ethers, polyoxyethylenealkylallyl ether sulfuric acid esters, amino and alkali salts of dodecvlbenzenesulfonic acid such as the dimethylethanolamine 10 salt of dodecylbenzenesulfonic acid and sodium dodecylbenzenesulfonic acid, and sodium dioctylsulfosuccinate. The polymerization typically proceeds by free radical polymerization. The free radical source is typically 15 supplied by a redox initiator or by an organic peroxide or azo compound. Useful initiators include, without limitation, ammonium peroxydisulfate, potassium peroxydisulfate, sodium metabisulfite, hydrogen peroxide, t-buryl hydroperoxide, dilauryl peroxide, t-butyl peroxybenzoate, 2,2' 20 azobis(isobutyronitrile), and redox initiators such as ammonium peroxydisulfate and sodium metabisulfite with ferrous ammonium sulfate. Optionally, a chain transfer agent may be used. Typical chain transfer agents include mercaptans such as octyl mercaptan, n- or tert-dodecyl 25 mercaptan, thiosalicylic acid, mercaptoacetic acid, and 19 qRt1RTITLITE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 mercaptoethanol; halogenated compounds; and dimeric aloha methyl styrene. Acrylic polymers prepared by emulsion polymerization can have weight average molecular weights of one million or more. 5 The weight average molecular weight of the acrylic dispersion is preferably from about 5,000 to about 5,000,000, more preferably from about 7500 to about 500,000, and even more preferably from about 10,000 to about 50,000. If prepared by solution polymerization and then dispersed in water, the 10 acrylic polymer will generally have a number average molecular weight of from about 5000 to about 60,000. The molecular weight can be determined by gel permeation chromatography using a polystyrene standard or other known methods. 15 The theoretical glass transition temperature of the acrylic polymer can be adjusted according to methods well known in the art through selection and apportionment of the comonomers. The acrylic polymer has a glass transition temperature that is at least about 20'C higher than the glass 20 transition temperature of polyurethane resin. Preferably, the acrylic polymer has a glass transition temperature that is at least about 40'C higher, more preferably about 50'C higher, than the glass transition temperature of polyurethane resin. In a preferred embodiment, the theoretical Tg of the 20 CilRqTITilTF RHFFT (RULE 2R) WO 01/36114 PCT/USOO/22919 acrylic polymer is between about -30 0 C and 80 0 C, more preferably between about -20 0 C and 40 0 C. The polyurethane polymer may be included in the thermosetting primer in an amount of at least about 40% by 5 weight, preferably at least about 50% by weight, based on the combined nonvolatile weights of the polyurethane polymer and the acrylic polymer. The polyurethane polymer may be included in the primer in an amount of up to about 98% by weight, preferably up to about 80% by weight, based on the 10 combined nonvolatile weights of the polyurethane polymer and the acrylic polymer. It is preferred to include from about 50% by weight to about 75% by weight, and even more preferred to include from about 65% by weight to about 75% by weight, of the polyurethane polymer, based on the combined 15 nonvolatile weights of the polyurethane polymer and the acrylic polymer. The thermosetting primer composition also includes a crosslinker component. The crosslinker component includes one or more crosslinkers reactive with active hydrogen 20 functionality, including any of those already described above as useful in the chip resistant primer composition. The crosslinker component preferably is from about 2% by weight to about 30% by weight, and more preferably from about 5% by weight to about 20% by weight, and particularly 25 preferably about 5% to about 15% by weight of the combined 21 SUBSTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 nonvolatile weights of the polyurethane, the acrylic polymer, and the crosslinking component of the thermosetting primer composition. The chip resistant primer compositions and thermosetting 5 primer compositions may include one or more catalysts. The type of catalyst depends upon the particular crosslinker component composition utilized. Useful catalysts include, without limitation, blocked acid catalysts, such as para toluene sulfonic acid, dodecylbenzene sulfonic acid, and 10 dinonylnaphthylene disulfonic acid blocked with amines; phenyl acid phosphate, monobutyl maleate, and butyl phosphate, hydroxy phosphate ester; Lewis acids, zinc salts, and tin salts, including dibutyl tin dilaurate and dibutyl tin oxide. 15 The chip resistant primer coating compositions and thermosetting primer coating compositions according to the invention may further include pigments such as are commonly used in the art, including color pigments, corrosion inhibiting pigments, conductive pigments, and filler 20 pigments. Illustrative examples of these are metal oxides, chromates, molybdates, phosphates, and silicates, carbon black, titanium dioxide, sulfates, and silicas. Other conventional materials, such as dyes, flow control or rheology control agents, and so on may be added to the 25 compositions. SUBSTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 The chiD resistant primer composition and the thermosetting primer composition may have a very low content of volatile of organic solvent. The polyurethane dispersion is prefferably prepared as a solvent free or substantially 5 solve- free dispersion. By "substantially solvent free" it is mean: that the dispersion has a volatile organic content of less than about 5% by weigh: of the primer composition. The acrylic dispersion is also preferably solvent free or substanaially solvent free dispersion. The primer 10 composition preferablv has a volatile organic content of less than about 1.5, more preferably less than about 1.3, and even more preferably less than about 0.7. The volatile organic content of a coating composition is typically measured using ASTM D3960. 15 The primer coating compositions of the present invention can be applied over many different substrates, including wood, metals, glass, cloth, plastic, foam, metals, and elastomers. They are particularly preferred as primers on automotive articles, such as metal or plastic automotive 20 bodies or elastomeric fascia. When the article is a metallic article, it is preferred to have a layer of electrocoat primer before application of the primer coating composition of -he invention. The composite coating of the invention has, as adjacent 25 layers, a first primer coating layer that is obtained by qI IR5RTITilTF qHEET (RULE 261 WO 01/36114 PCT/USOO/22919 appling tne cnip resistant primer composition of the invention and a second primer coating layer on top of the first primer coating layer that is obtained by applying the thermosetting crimer coating composition. The composite 5 coating has a :opcoa: -aver applied over one primer coating lavers. The topcoat aver may include a basecoat coating layer applied over the primer coating laver and an outer, clearcoat layer applied over the basecoat coating layer. Te composite primer coating layers of the invention is 10 acolied directy --o the substrate or over one or more other layers of primer, such as the electrocoat primer. The applied primer coating compositions are then baked and, at least in the case of the thermosetting primer composition, cured to form a primer coating layer. The electrocoat primer 15 or other first layer of primer may be cured at the same time as the primer coating layers of the invention are baked in a process known as "wet-on-wet" coating. The composite primer coating savers formedd from ohe primer coating compositions of the Invention are the outermost primer layers of he 20 composite coating. A copcoat composition is applied over the primer coating lavers and cured to form a topcoat layer. The substrate at hat ioint i nen covered w7th a composite coating that has at least the two lavers of primer coatino derived from the 25 inventive compositions and at least one layer of topcoat. In qIIRRTITUTF SHEET (RULE 261 WO 01/36114 PCT/IUSOO/22919 a Referred embodiment, the coating composition of the present invention is overcoated with a topcoat applied as a color-plus-clear (basecoat-clearcoat) topcoat. In a basecoat-clearcoat topcoat, an underlayer of a pigmented coating, the basecoat, Is covered with an outer laver of a transparent coating, the clearcoat. Basecoat-clearcoat toccoats provide an atractive smooth and glossv finish and generally improved performance. Crosslinking compositions are prererred as the topcoat 10 layer or layers. Coatinqs of this type are well-known in the art and include waterborne compositions as well as solventborne compositions. For example, the topcoat may be a clearcoat according to U.S. Pat. No. 5,474,811, applied wet on-wet over a layer of a basecoat composition. Polymers 15 known in the art to be useful in basecoat and clearcoat compositions include, without limitation, acrylics, vinyl, polvurethanes, polycarbonates, polyesters, alkyds, and pclysiloxanes. Acrylics and polyurethanes are preferred. Thermoset basecoat and clearcoat compositions are also 20 preferred, and, to that end, preferred polymers comprise one or more kinds of crosslinkable functional groups, such as carbamate, hydroxy, isocyanate, amine, epoxy, acrylate, vinyl, silane, acetoacetate, ant so on. he olymer may be self:-crosslinking, or, preferably, the composition may 25 include a crosslinking agent such as a polyisocyanate or an SUBSTITUTE SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 aminoplast resin of the kind described above. In one embodiment, waterborne basecoat compositions and/or clearcoat compositions having low volatile organic content are used. The waterborne basecoat and waterborne clearcoat compositions 5 each preferably has a volatile organic content of less than about 1.5, more preferably less than about 1.3, and even more preferably less than about 0.7. Each layer of the composite coatings of the invention can be applied to an article to be coated according to any of 10 a number of techniques well-known in the art. These include, for example, spray coating, dip coating, roll coating, curtain coating, and the like. If an initial electrocoat primer layer is applied to a metallic substrate, the electrocoat primer is applied by electrodeposition. For 15 automotive applications, the primer coating compositions of the invention and the topcoat layer or layers are preferably applied by spray coating, particularly electrostatic spray methods. CoatinQ layers of about one mil or more are usually applied in two or more coats, separated by a time sufficient 20 to allow some of the solvent or aqueous medium to evaporate, or "flash," from the applied layer. The flash may be at ambilent or elevated temperatures, for example, the flash may use radiant heat. The coats as aolied can be from 0.5 mil up to 3 mils dry, and a sufficient number of coats are 25 applied to yield the desired final coating thickness. 26 qIIRqTITUTF SHEET (RULE 261 WO 01/36114 PCT/USOO/22919 e chip resistant former laver, whicn s formed from the chip resistant primer composition, may be from about 0.5 mil to about 3 mils thick, preferably from about 0.8 mils to about 1.5 mils thick. 5c outermost prmer layer, which is formed by reactinc the thermosettlinc former compositions of the invention, may be cured bv reaction of curing component w at least one the polyurethane resin or the acrylic resin. before the toocoa: is arpied. The cured primer layer may be from about 10 0.5 mi: to abouc 2 mils thick, preferably from about 0.8 miles to about 1.2 mils thick. Color-plus-clear topcoats are usually applied wet-on wet. The compositions are applied in coats separated by a flash, as described above, with a flash also between the last 15 coat of the color composition and the first coat the clear. The two coating layers are then cured simultaneously. Preferably, the cured basecoat layer is 0. Eo 1.E miles thick, and the cured clear coat layer Is 1 co 3 mils, more preferably 1.6 to 2.2 mils, thick. 20 Alternativelv he primer layer(s) of the invention and the tcoat can ce acelied "wet-on-we'." For example, the chic resistant crime comoosition cf he invention can ce appi=ea, then the appli:d layer flashed; crenthe :opcoac can be applied and flashed; the chermosetting primer composition 25 of the invention can be applied, then the applied layer SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 flashed; then the topcoat can be applied and flashed then the thermosetting primer, optionally the chip resistant primer (if it is thermosetting) and the topcoat can be cured at the same time. Again, the torcoat can include a basecoat layer 5 and a clearcoat layer applied wet-o-wet. The thermosetting coating compositions described are preferably cured with heat. Curing temperatures are preferably from about 70 0 C to about 1800C, and particularly preferablv from about 170OF to about 200OF for a composition 10 including an unblocked acid catalvst, or from about 240OF to about 275 0 F for a composition including a blocked acid catalyst. Typical curing times at these temperatures range from 15 to 60 minutes, and preferably the temperature is chosen to allow a cure time of from about 15 to about 30 15 minutes. In a preferred embodiment, the coated article is an automotive body or part. The composite primer layers of the invention provide improved chip resistance as compared 7: previously known primers, while retaining the desirable properties of 20 sandability and corrosion resistance. Further, the primer comosotions o the invention can be formulated to have low volatile organic content and even no volae organbc content. The invention is further described in the following 25 examples. The examples are merely illustrative and do not in 2S SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 anv wav limit :ne scoce of ne invention as aescribed and claimed. All parts are by weight unless otherwise indicated. Examples Example 1. Precaration of a Pigment Paste A cigmen: caste was prepared hy grinaing a p BAYHYDROL 140 AQ polyuechane dispersi on acout 40% nonvolat1le , 9% water, and is :oluene, glass transiin temperature of about -450C, pH of about 6.0 to about 7.3, weight average molecular weight cf about 25,000, anionic 10 Desmodur W/1,,6-hexamethylene diisocyanate/polvester pCvol based polyurethane, available from Bayer Corporation, Pittsburgh, PA), titanium dioxide, barium sulfate extender, and carbon black on a horizontal mill to a fineness of 6 microns. The pigment paste was 63% by weight nonvolatile in 15 water. The nonvolatiles were 33.1% by weight of BAYHYDROL 140 AQ, 33.1% by weight of titanium dioxide, 33.1% by weight Of carium sulfate extender, and the balance carbon blackc. Example 2. Chi Re-sistant Area Primer Composiion A chic resistant crimer comcosition was crecarea cy 20 mixing together 219.6 parts by weight of the Pigment Paste of Example 1, 212.4 parts by weicht cf BAYHYDROL 140 AQ, 98.02 carts bv weight of deionized water, and . carlts by weight of thickenermareri. nTe comcostcon was adjusted c 91 cenoipoise with the addition of 22 grams of water. SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 Example 3. Chit Resistant Area Primer Comnosition A chip resistant primer composition was prepared by mixing together 219.6 parts by weight of the Pigment Paste of Example 1, 179.6 parts by weight of BAYHYDROL 140 AQ, 82.95 tcarts C weight of deionized water, 1. parts by weigh: of RESOMENE 747 (a melamine formaldehyde resin available from Solria, St. Louis, MO), 0.43 parts by weiht of AEEX EP 110 (anionic surfactant available from Rhodia), and 3.45 parts by weight of a <hickener material. The composition was adjusted 10 to 92 cenicoise with the addition of 22 grams of water. Example 4. Thermosetting Primer Composition A primer composition was prepared by first mixing together 17.51 parts by weight of BAYHYDROL 140 AQ polyurethane dispersion, 16.27 parts by weight of an emulsion 15 of an acrylic polymer (glass transition temperature of 20 'C., nonvolatile content of about 41% in water, acid number of about 8 mo KOH/g nonvolatile, hvdroxyl equivalent weign: of 51~, salted with 2-am:no-2-methpvropanol to a pH of abour 6 to 7), 20.9 tarts deionized water, and 40.89 parts v weight 20 of the pigment paste of Example 1. To this mixture were added 2.71 tarts by weich: of RESIMENE 747 and 0.27 tarts bv wenont of AEX E 110. A total of 1.39 tarts by weigh: of an additive package (defoamer, wetting agent, ana tnnoxener was then added. Finally, the pH of the primer composition was 25 adjusted to about 8.0 with 2-amino-2-methylpropanol. 30 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 The measured volatile orqanic content of the primer composition is 0.24 pounds per gallon. The primer composition had a nonvolatile content of 42% by weight. The primer composition was adjusted before spray application with 5 deionized water to a viscosity of 7 to 110 centipoise. The primer composition of Examples 2 and 3 was applied to eleccrocoat primed 4"x12" steel panels. Before curing the first primer layer, the primer composition of Example 4 was applied over the first primer layer on each panel. Both 10 primer layers were cured together according to the bake schedule shown in the table below to form a composite primer. Each of the primer layers was about 1.0 mil thick. The cured composite primer was then topcoated with commercial basecoat and clearcoat compositions. 15 As comparative example, a panel was prepared by applying the primer composition of Example 4 directly to an electrocoat primed 4"x12" steel panel. The primer layer was cured and topcoated with commercial basecoat and clearcoat compositions as before. 20 As another comparative example, a panel was prepared by applying a layer of a commercial chit resistant primer, U26AW415K and a layer of a commercial thermosetting primer, U28AW032, both available from BASF Corporacon, Southfield, MI. Both primer layers were cured together according to the 25 bake schedule shown in the table below to form a composite 31 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 crimer. Eac 2f the -crimer savers was about 1.0 mil thick. The cured composite primer was then oopcoated with commercial basecoat and clearcoat compositions. The canels were then subjectec to gravelometer testing according co one oes procedure - SAE J400, except: tha: three 2pins of gravel were used instead of: -he one pino soecified b- rne :eso meonod. Briefly, in the SAE J400 procedure, the panels are cooled to -20 centigrade for I hour prior ce the gravel test. The panel Is positioned in a 10 gravelomeer nachine in an npright position, 90 degrees from path of gravel. One pint of gravel is blown onto the panel with an air pressure of 70 psi. [In testing the examples of the invention, three pints of gravel were used.] The panel is then warmed to room temperature, tape pulled with 3M 898 15 strapping tape, and rated according to chip rating standards on a scale of 0 to 9, with 0 corresponding to a standard having cotal delaminacion of :he coating and 9 corresponding to a standard having almost o chips. The gravelometer ratings for the panels obtained using 20 the comoositions of Examoles i and 2 are shown in the following table. SAE 400 Gravelometer Ratings, using tints travel Primer _avers_ 1 Minuoes a: 30 Minuoes at 27 T OF Sake 325F F ake Example 2/Example Example 3/Example 4 +/5 Example 4 oniv 7- 6 U26AW415K/U28AW032 6 5 SIRSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 The invention has been described in detail with reference to preferred embodiments thereof. It should be understood, however, that variations and modifications can be 5 made within the spirit and scone of the invention. 33 SUBSTITUTE SHEET (RULE 261

Claims

1. A method of coating a substrate, comprising steps of: (a) applying a layer of a chip resistant primer composition, wherein said chip resistant primer composition comprises as a resinous portion a polvurethane polvmer having a glass transition temperature of 0 0 C or less and, optionally, a second component that has reactive functionality; (b applying over the layer of the chip resistant primer 10 composition a layer of a thermosetting primer composition, wherein the thermosetting primer composition comprises a polyurethane polymer having a glass transition temperature of 0*C or less, an acrylic polymer having a glass transition temperature that is at 15 least about 20'C higher than the glass transition temperature of said polyurethane polymer, and a crosslinking component that is reactive with at least one of the polyurethane polymer and the acrylic polymer; and 20 (c, applying over the layer of the thermosetting primer comoosition at least one layer of a copcoat composition, wherein the reactive functionality of the second component is reactive with at leaso one oolymer selected from the group consisting of the polyurethane polymer of the chip resistant 25 primer composition, the polyurethane polymer of the 34 SUBRTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 thermosetting primer composi=Lon, -- he a ic polymer of the thermosetting primer composition, and combinations thereof.

2. A method according to claim 1, wherein the chip 5 re n orimer comoosition is not baked before the thermosett:ing rimer composition is applied.

3. A method according to claim 1, wherein the chip resistant primer composition is baked before the 10 thermosetting primer composition is applied.

4. A method according to claim 1, wherein the thermosetting primer composition is not cured before the topcoat composition is applied, and the thermosetting primer 15 composition and topcoat composition are cured together.

5. A method according to claim 1, comorising a step of applying said chip resistant primer coating composition over a layer of an electrocoat primer. 20

6. A method according to claim 1, wherein toe topcoat coating composition comprises a basecoat coazing composi:ion and a clearcoat coatinc composition. SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919

7. A method accordinc toca , wrerein rhe suostraze is metal or Dlastic.

8. A method according to claim I, wherein said substrate is an automoiv eceoav.

9. A method according oc m , wherein sad chip resistant primer composition is applied to an area of said automoive vehicle body selected from the group consisting of 10 the iars, che fron: edge of the roo:, the leading edge of the hood, the front bumper, the rocker panels, and combinations thereof.

10. A method according to claim 1, wherein the polyurethane 15 of the chip resistant primer coating composition and the polyurethane of the thermosetting primer coating composition are the same.

11. A method according to claim I, wherein the chip 20 resistant primer coating composition and the thermosettinq primer coating comnosi:on are oC=' aqueous.

12. A method according to camm , erein the chip resisant primer coatIng compositI:n includ-e7 toe second 25 component. :6 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919

13. A method according to claim 12, wherein the second component is an aminoplast resin. 5

14. A method acccrdinc to clai ~3, wherein the aminoplast resin is a melamine formaldehyde resin.

15. A method according to claim 14, wherein the melamine formaldehyde resin Is reactive :ith the acrylic resin of the 10 thermosetting primer coating composition.

16. A method according to claim 10, wherein the polyurethane polymer has a glass transition temperature of about -20 0 C or less. 15

17. A method according to claim 10, wherein the polyurethane polymer has a glass transition temperature of about -30 C or _eS. 20

18. A method according to claim 10, wherein the polvurethane polvmer has a glass transition emnerature of about from about -ZOC cc about .

19. A method according to claim 10, wherein the polyurethane 25 polymer is the reaction product of a polyester polyol and a 37 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919 polyisocyanate selected from the group consisting of methylene-bis-4,4'-isocyanatocyclohexane, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, and combinations thereof.

20. A method according to claim 10, wherein the polyurethane polvmer has a weight average molecular weight of from about 15,000 to about 60,000. 10

21. A method according to claim 10, wherein the polyurethane polymer is present in the aqueous coating composition as an anionic dispersion.

22. A method according to claim 1, wherein the acrylic 15 polymer has a glass transition temperature of from about 20'C to about 40'C.

23. A method according to claim 15, wherein the acrylic polymer has a hydroxyl equivalent weight of 1000 or less. 20

24. A method according to claim 12, wherein the second component is included in the resinous portion of the chi resistant primer In an amount of from about 2% by weict to about 30% by weight. 25 38 SUBSTITUTE SHEET (RULE 26) WO 01/36114 PCT/USOO/22919

25. A method according to claim -, wherein the polyurethane polymer of the thermosetting primer coating composition is from about 40% by weight to about 80% by weight of the combined nonvolatile weights of the polyurethane polymer and 5 the acrvlic polvmer of the thermosetting primer coating comoos:iion.

26. A method according to claim 1, wherein each of the primer compositions has a volatile organic content of less 10 than about 0.7 pounds per gallon.

27. A composite coating produced according to the method of claim 1. 39 IJRqTITUTE SHEET (RULE 26)